Transcutaneous electrical nerve stimulation (TENS) is the delivery of electricity across the intact surface of the skin to activate underlying nerves; generally with the objective of pain relief. An electrical circuit generates stimulation pulses with specified characteristics. One or more pairs of electrodes, placed on the user's skin, transduce the electrical pulses and thereby stimulate underlying nerves in order to trigger an analgesic response.
Pain relief from TENS stimulation often begins within 15 minutes of the stimulation onset and may last up to an hour following the completion of the stimulation period (also known as a “therapy session”). For optimal pain relief, each therapy session should run for at least 30 minutes and preferably 60 minutes. To maintain pain relief (i.e., analgesia), TENS therapy sessions typically need to be initiated at regular intervals, such as every other hour. Newly developed wearable TENS devices such as the QUELL® device by Neurometrix, Inc. of Waltham, Mass., USA provide users with an option to automatically restart therapy sessions at pre-determined time intervals.
Battery life is an engineering challenge in portable devices. The waveform of the stimulation pulse has a significant impact on the battery life of a TENS device. Symmetric biphasic rectangular pulses are often used in TENS devices but such pulse waveforms may not be optimal for maximizing battery life.
The present invention is directed to TENS devices which utilize novel stimulation waveforms and novel arrangements of TENS electrodes to improve the efficiency of power consumption while enhancing therapeutic effects.